ALBANY — Gov. Andrew Cuomo vowed Wednesday to impose a teacher evaluation system on New York City if Mayor Michael Bloomberg and the teachers union can't agree on one.

Conflict between the mayor and the United Federation of Teachers has already cost city schools $250 million in state aid and millions more in federal aid for the past year. The evaluations are required under a federal grant aimed at improving instruction and by a 2010 law pushed by Cuomo, but New York City failed to reach an agreement by the Jan. 17 deadline.

Now Bloomberg and the UFT have until September to create an evaluation system for teachers and principals or lose another annual increase in state aid of at least $200 million and more federal aid. "The impasse must be resolved," the Democratic governor said Wednesday. He would direct the state Education Department to devise a system, then impose it on New York City's 75,000 teachers.

The union had blamed Bloomberg for "intransigence" in talks. "While we would prefer a negotiated settlement, it's good to know that should the talks fail again, people who actually understand education will be part of the decision-making process," said Michael Mulgrew, UFT president. "Parents need to know that, thanks to the governor and the legislative leaders, there will be no further risk of the loss of state money for our schools."

Bloomberg had told lawmakers on Monday in Albany that the UFT had no interest in creating evaluations and that the penalty for failing to agree on a system only hurts students.